Deutscher Tropentag, October 9 - 11, 2002 in Kassel-Witzenhausen "Challenges to Organic Farming and Sustainable Land Use in the Tropics and Subtropics"

Performance of Narrow Strips of Vetiver Grass (Vetiveria zizanioides) and Napier Grass (Pennisatum purpureum) as Barriers against Runoff and Soil Sediment Loss on a Clay Loam Soil (Andosol) in Kenya

¹University of Agricultural Sciences (BOKU), Crop Production and Plant Breeding, Austria
²University of Agricultural Sciences (BOKU), Austria

Abstract

Runoff plots were used to investigate the performance of narrow strips of Vetiver grass and Napier grass as barriers against runoff, sediment, and nutrient loss in a clay loam soil in Tatton farm of Egerton University, Kenya, between January 2000 and August 2001. The amount of sediment, runoff, and nutrients (total inorganic nitrogen and orthophosphorous) from the plots, depth of sediment deposition along the strips and growth rate of the strips were measured. A total of nine runoff plots, each measuring 16 m long by 2 m wide were used. The study site had an average slope of 8% and the grass strips were located at the lower end of the plots. The experiment was a randomized complete block design having three blocks with Napier grass strip, Vetiver grass strips and control (no grass strip) as the treatments. Compared to the control the runoff from the Napier grass strip plots and the Vetiver grass strip plots averaged 46% and 88% respectively, while the sediment loss from the plots averaged 8% and 62% respectively. Compared to the control the deposition of soil sediment along Napier and Vetiver grass strips was significantly higher. But the difference between Napier grass and Vetiver grass was only significant in the first year of the study (2000). The barriers significantly reduced the loss of Nitrate-nitrogen (NO₃-N) and Ammonium-nitrogen (NH₄-N) from the plots compared to the control. Napier grass strip barrier reduced the loss of NO₃-N and NH₄-N by 45% and 47% respectively while Vetiver grass reduced the loss of NO₃-N by 11% but had no effect on NH₄-N. The effect of the barriers on Orthophosphorous (PO₄-P) and Nitrite-nitrogen (NO₂-N) was not significant. The growth rate in width and height of Napier grass strip was 84% and 36% respectively, higher than that of Vetiver grass. Napier grass was more effective in reducing runoff, sediment and nutrients loss under the conditions of the study due to its faster growth rate that enabled it to form an effective barrier much faster than the Vetiver grass.

Keywords: Grass strips, Pennisatum purpureum, runoff, sediment, Vetiveria zizanioides

Contact Address: James Owino, University of Agricultural Sciences (BOKU), Crop Production and Plant Breeding, Donaufelderstraße 54 / 4317, 1210 Wien, Austria, e-mail: joowinyahoo.com